1. Field of the Invention
This invention relates to lubricant compositions having improved load carrying, antiwear and extreme pressure properties. In one of its aspects, the invention relates to lubricant compositions in the form of such organic media as oils of lubricating viscosity and greases thereof to which it is desired to impart such properties. Of particular significance is the improvement in a wide variety of metal working fluids, which include both the oleaginous, aqueous and emulsion types. Such metal working fluids are generally utilized for lubricating metals during processing operations such as grinding, drawing, rolling, cutting, forging and the like.
2. Description of the Prior Art
U.S. Pat. No. 2,470,276 of Watkins teaches that the presence of even small amounts of elemental sulfur in petroleum oils is highly objectionable because of its corrosive action with respect to copper and that a number of processes are available for the removal of sulfur from such oils. Since such processes are not completely effective in removing sulfur, Watkins provides a method for inhibiting sulfiding of metallic copper by the sulfur present in petroleum oils. Briefly, the method includes incorporating small amounts, e.g., 0.006 to .2 volume percent, of a hydrocarbon hydroperoxide, such as tertiary butyl hydroperoxide into the oil in order to inactivate the sulfur contained therein.
The petroleum compositions disclosed by Watkins as non-corrosive to copper contain 0.034 weight percent sulfur and 0.006 to .2 volume percent hydroperoxide. The Watkins compositions are different from those disclosed and claimed herein in that they contain different types and amounts of sulfur and do not exhibit the improved load carrying properties as do the compositions of the present invention.
In U.S. Pat. No. 3,012,967, Leonardi et al. teach the stabilization of mineral lubricating oils against the deleterious effects of oxidation by incorporating therein a small amount of each of (1) an aromatic hydroperoxide having a hydroperoxy group attached to an alpha carbon atom of an aryl nucleus thereof, and (2) an acid whose dissociation constant in water is at least about 1.0 .times. 10.sup.-5.
As one skilled in the art would be aware, the acid present in the Leonardi compositions would readily react with the aromatic peroxides to form phenols. The conversion of cumene hydroperoxide into phenol is described in Morrison and Boyd, Organic Chemistry, Second Edition, (Boston : Allyn and Bacon, Inc., 1970), page 794. Such reaction would not occur in the compositions of the present invention, since no acid is present. Further, Leonardi does not disclose the incorporation of sulfur into the described compositions.
Finally, in U.S. Pat. No. 3,607,748, Wilson et al. provide a process for preparing lubricating oil compositions which have improved oxidation resistance. The process taught therein comprises (1) oxidizing a hydrocarbon material with an oxidant and (2) contacting the oxidized hydrocarbon material from step (1) with hydrogen sulfide. In carrying out the oxidizing step, oxidants such as oxygen (including air) and an organic hydroperoxide are utilized. When organic hydroperoxides are employed, they are blended into the hydrocarbon material in concentrations of from about .2 to about 10 moles of hydroperoxide per mole of oxygen incorporated into the hydrocarbon material. The Wilson et al. process increases the oxygen content of the hydrocarbon material from about .10 to about 10 percent, by weight.
In Ellis, The Chemistry of Petroleum Derivatives, (New York : The Chemical Catalog Company, 1934), page 900 it is taught that peroxides, such as produced by step (1) of the Wilson et al. process, react with reducing agents (hydrogen, hydrogen sulfide, mercaptans) to form either glycols or substituted ethylene oxides. Thus, in order to stabilize oils against future oxidation, Wilson teaches first oxidizing those compounds present in the oil which would be susceptible to oxidation. Next, the deleterious peroxide and hydroperoxides produced are converted to glycols or substituted ethylene oxides.
Wilson, as does Leonardi et al., provides for the incorporation of hydroperoxides into lubricants only to serve as a starting material for further in situ reactions. Such is not the situation in the present invention, where the presence of the sulfur and hydroperoxide in the lubricant composition impart unexpected load carrying ability.